 default namespace = "http://eric.van-der-vlist.com/ns/library"
 
 element library
 {
    element book
    {
       attribute id { text },
       attribute available { text },
       element isbn { text },
       element title { attribute xml:lang { text }, text },
       element author
       {
          attribute id { text },
          element name { text },
          element born { text },
          element dead { text }?
       }*,
       element character
       {
          attribute id { text },
          element name { text },
          element born { text },
          element qualification { text }
       }*
    }+
 }
